Told I owe money back on my benefits (update)

After 15 weeks of benefits I got a notice saying I must repay some of it. I would rather hear the honest version than the polite one. I did not notice any errors at the time. Has anyone disputed one of these?

Keep everything in writing and save the confirmation numbers. It saved me later.

I asked for a waiver and a plan in the same call, and they gave me both forms. It was less scary than I expected.